We own a 2006 190 Versatile RT equipped with the 6.0 standard, and we ordered it with the optional locking rear differential & transmission cooler. These options were important to me. I don't know about now, but in 2006, if you wanted the locking rear differential, you had to also take the 410:1 rear gears, as the 373:1 was the standard. I questioned RT about this in detail because although I wanted the locking rear, I really was leary of the 410 gears, as I felt I would sacrifice my MPGs by going to the lower gears. They assured me that they had done testing on that very thing, and that the 6.0 & 410 gears would have minimal impact on my mileage, but would deliver exceptional performance in all kinds of terrain situations. Frankly I was very skeptical that could be the case, but I wanted the locking rear gears so I went along with the lower 410 gear vs. the 373 gears which was not available with the locking rear gears. After 4-years of use, I can tell you that RT was absolutely correct. We have never lacked for power in any situation that we have used our trek in, including trailer towing, mountains etc. Our transmission rarely has to down shift when climbing grades, except in very extreme grades. We normally get 15 to 19 MPG on our trips. In my view, the 6.0 coupled to the 410 rear end is an outstanding performer. I have experience with both 5.0 & 5.7 V-8s on conversion vans that did not weight near what the loaded RT does, and their performance was marginal at best and the MPGs were worse than what we get with the trek. I really believe that unless all of your travels are on completely flat roads, you will be dissapointed in the power from the 4.8, and You will definately be dissapointed in the performance in any mountains. Any time you get into situations where your transmission is constantly down shifting to compensate for lack of engine power, you will not get good mileage, and your Class B is not going to perform like you need it to. Engines & transmissions work harder in those situations, which means higher wear and tear & heat, and lower MPGs. I would never make the choice to trade good overall performance for hoping to get better fuel economy out of a smaller engine. We arn't talking about a Toyota or Honda or some small car here, it is a big heavy unit. I really believe that any of the Class B manufacturers that use the 4.8 in place of the 6.0 are going to find that they have plenty of complaints down the road. I hope you are happy with which ever choice you elect to go with, and best of luck to you.